Orthoceras is an extinct cephalopods related to modern squid, octopus, and Nautilus. They are characterized by long, straight, conical shells, tentacles and the ability to use jets of water for locomotion.
They first appeared in the early Ordovician period about 488 million years ago.
Orthoceras disappears from the fossil record during the lower Triassic Period about 200 million years ago.
approximate measurements: 1 1/2 - 2 x 1-2 wide